Highly quenchable Fe-based rare earth materials for ferrite replacement

Abstract

The present invention relates to highly quenchable Fe-based rare earth magnetic materials that are made by rapid solidification process and exhibit good magnetic properties and thermal stability. More specifically, the invention relates to isotropic Nd—Fe—B type magnetic materials made from a rapid solidification process with a lower optimal wheel speed and a broader optimal wheel speed window than those used in producing conventional magnetic materials. The materials exhibit remanence (B r ) and intrinsic coercivity (H ci ) values of between 7.0 to 8.5 kG and 6.5 to 9.9 kOe, respectively, at room temperature. The invention also relates to process of making the materials and to bonded magnets made from the magnetic materials, which are suitable for direct replacement of anisotropic sintered ferrites in many applications.

1. A method of making a magnetic material comprising:
 forming a melt comprising the composition, in atomic percentage, of
   (R 1−a R′ a ) u Fe 100−u−v−w−x−y Co v M w T x B y   
 
  rapidly solidifying the melt to obtain a magnetic powder; 
 thermally annealing the magnetic powder at a temperature range of about 350° C. to about 800° C. for about 0.5 minutes to about 120 minutes; 
 
       wherein R is Nd, Pr, Didymium (a nature mixture of Nd and Pr at composition of Nd 0.75 Pr 0.25 ), or a combination thereof; R′ is La, Ce, Y, or a combination thereof; M is one or more of Zr, Nb, Ti, Cr, V, Mo, W, and Hf; and T is one or more of Al, Mn, Cu, and Si, wherein 0.01≦a≦0.8, 7≦u≦13, 0≦v≦20, 0.01≦w≦1, 0.1≦x≦5, and 4≦y≦12, and
 wherein the magnetic material exhibits a remanence (B r ) value of from about 6.5 kG to about 8.5 kG and an intrinsic coercivity (H ci ) value of from about 6.0 kOe to about 9.9 kOe. 
 
     
     
       2. The method of  claim 1 , wherein the rapidly solidifying comprises a melt-spinning or jet-casting process at a nominal wheel speed of from about 10 meter/second to about 60 meter/second. 
     
     
       3. The method of  claim 2 , wherein the nominal wheel speed is from about 35 meter/second to about 45 meter/second. 
     
     
       4. The method of  claim 3 , wherein an actual wheel speed is within plus or minus 30% of the nominal wheel speed. 
     
     
       5. The method of  claim 4 , wherein the nominal wheel speed is an optimum wheel speed used in producing the magnetic material by the rapid solidification process, followed by the thermal annealing process. 
     
     
       6. The method of  claim 4 , wherein the actual wheel speed is within plus or minus 25% of the nominal wheel speed. 
     
     
       7. The method of  claim 4 , wherein the actual wheel speed is within plus or minus 20% of the nominal wheel speed. 
     
     
       8. The method of  claim 4 , wherein the actual wheel speed is within plus or minus 15% of the nominal wheel speed. 
     
     
       9. The method of  claim 4 , wherein the actual wheel speed is within plus or minus 10% of the nominal wheel speed. 
     
     
       10. The method of  claim 4 , wherein the actual wheel speed is within plus or minus 5.0% of the nominal wheel speed. 
     
     
       11. The method of  claim 4 , wherein the actual wheel speed is within plus or minus 1.0% of the nominal wheel speed. 
     
     
       12. The method of  claim 4 , wherein the actual wheel speed is within plus or minus 0.5% of the nominal wheel speed.